Rocky Road

Sam Kean

Artist’s rendering of Jovian Trojans, asteroids that follow the same orbit as Jupiter around the sun. (Courtesy NASA/JHUAPL)

Earth is not a great representative of the periodic table. Ninety percent of all atoms in the universe are hydrogen atoms, which obviously doesn’t hold true down here. And there is subtler elemental skewing as well: various transition metals in the middle of the periodic table—platinum, gold, rhodium, palladium, iridium, osmium, and others—are rare enough across the cosmos, but they’re rarer still in Earth’s crust. Those elements don’t bond well with carbon, oxygen, sulfur, and other rock-forming elements. Instead they’re siderophiles—iron lovers—and they mostly got drug down into Earth’s molten iron core long ago. The high prices those elements fetch—platinum goes for $20,000 per pound—reflects their rarity and reflects the fact that we’re always searching for more.

We may have found it. Because of the slavish devotion of siderophile metals to iron, there is another source out there—way out there, inside iron-rich asteroids. Asteroids might seem as inaccessible as Earth’s core, but a few new companies—backed by tech billionaires and buoyed by the recent success of private spaceflight—have announced plans to mine asteroids and drag the booty, especially platinum, back to Earth. Some asteroids have platinum concentrations twenty times richer than ore mined on Earth, which could lead to billions in profits. One company calculated that even a modest asteroid (1,600 feet wide) could liberate more platinum and certain other metals than human beings have ever mined in history.

(And—pssst—don’t tell the investors, but even in the likely event that this scheme goes bust, the rest of us should encourage it because attempting to mine asteroids would be an immeasurable boon to science.)

First, the logistics. Within the next two years at least one of these astromining companies plans to launch telescopes (for a modest $10 million each) to scour the heavens for promising candidates among the tens of thousands of known asteroids within 30 million miles of Earth. “Promising” here means asteroids on easy-to-reach orbits and rich in platinum. Companies would then launch multipurpose probes toward those candidates to start chewing through ore and smelting. Space cruisers would presumably rendezvous with them later and haul the ore to Earth.

Some of the details remain hazy, though. One question is whether to mine and smelt in deep space, or drag the asteroid back toward Earth first (perhaps with magnets) and park it at a “Lagrange point,” where the competing gravitational tug from Earth and the moon would hold it steady. We also don’t know whether smelting or other processes would differ in zero gravity. So perhaps the probes would need to beam back chemical analyses, allowing scientists to find similar rocks among our terrestrial stock of meteors and launch them into space for testing. Finally, the scheme’s boosters seem to be gliding over one basic law of economics, that scarcity determines price. Flooding the world market with platinum would presumably depress profits.

But the beauty of the venture is that the investors are risking their own money: the rest of us risk zero and can only benefit. As one writer said, “This space-mining venture is either going to be a spectacular success or a spectacular failure. Either way, the emphasis will be on spectacular.” And even a complete flop from an entrepreneurial perspective could still lead to spectacular science.

Human probes have landed on asteroids twice before, in 2001 and 2005. One spacecraft even brought back samples—but only a few grains of dust. Any mining operation would bring back orders of magnitude more material, even as waste products. This bounty would benefit geochemists especially: asteroids formed at the same time and from the same space dust as Earth would provide valuable information about the raw materials of that process. Biochemists could also examine space rocks for amino acids and other chemicals vital for life.

What’s more, many asteroids contain loads of ice, and companies are also considering how to develop that resource. Analyzing that ice could provide clues about whether asteroids and comets originally filled our oceans with water. An even more exciting possibility would be not bringing the water down to Earth but learning how to exploit it in space. Astronauts could drink the water or split it into oxygen and hydrogen, both potent rocket fuels. Similarly, we could use asteroidal iron to build spaceships already in orbit, cutting down on the cost of launching from Earth’s gravity well.

Almost by accident, the mad dash for gold, silver, and other riches in the New World spurred a scientific and technological revolution a few centuries ago. The rush for profits in deep space could spur similar advances (hopefully without all the collateral pillaging and death this time). If so, studying the chemical properties of asteroids—once a rarefied pursuit—could rocket humanity out of its post-Apollo space doldrums.